Compact escalator steps used world-wide today exhibit fracture loads of 20 to 25 kilonewtons for a centrally applied load. In individual special cases of application, appropriate specifications may demand that the fracture load limit must lie at 2.5 tonnes for a force application at any desired place of the tread surface.
In the case of force application at any desired place of the tread surface, the afore-mentioned fracture load levels are not reached and supported by normal compact steps, because particularly high forces in the region of the step roller bearing result from such loads and this part of the compact step is not dimensioned for such a degree of loading. To fulfill this requirement, new constructions for compact steps and thus new, expensive die-casting molds must be created. The consequence of such a solution would be very high costs for a small number of pieces and thus substantially higher installation costs for an escalator of this kind.
Another solution consists of an appropriately stronger step being assembled in a different manner, utilizing a compound mode of construction, thus requiring different parts and materials. A step of the afore-mentioned kind is shown in U.S. Pat. No. 2,570,135. The step body is assembled from longitudinal and transverse carriers, front metal plate and tread plate. Guide and carrying rollers are screw-fastened by their bearing blocks at the longitudinal carriers. With use of appropriately dimensioned parts, a sufficiently strong tread step can in principle be produced in this manner. However, the manufacturing costs of such a step becomes so high that alternative solutions are needed.
It is therefore the object of the present invention to create an escalator tread step for higher fracture loads, which does not exhibit the disadvantages of the afore-mentioned solutions and for which existing constructions can be further used as far as possible.
The invention distinguishes itself in that an available compact step may be used in unchanged form as starting product, to which reinforcing elements for additional longitudinal and transverse stiffening are fastened at appropriate places.
The reinforcing elements for each step may be a bent-over section and a respective side plate with an encompassing rim, which are screw-fastened to the compact step at places to be reinforced. The reinforcing elements may be screw-fastened in force-lockingly manner at surfaces of existing ribs and webs of the compact step. Apart from the drilling of a few holes and the cutting of a pair of threads, no further adapting operations need be applied to the existing compact step. In particular, the reinforcing ribs that are present can remain in their original shape and maintain their function.